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Web Platform APIs

Web Platform APIs

The browser APIs beyond the document — fetch, storage, observers, workers — the layer that turns 'I can manipulate the page' into 'I can ship an app'.

~ 155 min·10 lessons·updated apr 2026

What you'll learn


Lessons

Read in order. Each lesson stands on its own, but the order is deliberate.

10 lessons · ~145 min total

  1. 01
    fetch in depth
    Requests, responses, headers, JSON vs text vs blob, and the error handling that nobody tells you about.
    16 min
  2. 02
    AbortController and cancellation
    One signal cancels them all — fetch, listeners, observers, timers.
    13 min
  3. 03
    URLs and search params
    Building query strings without bugs. URL, URLSearchParams, and the encoding traps.
    13 min
  4. 04
    The History API
    pushState, replaceState, popstate — client-side routing in fifty lines.
    14 min
  5. 05
    Storage
    localStorage, sessionStorage, cookies — quotas, JSON-in-a-string, and what each one is actually for.
    13 min
  6. 06
    IndexedDB
    When localStorage runs out. The object-store model, in plain words.
    17 min
  7. 07
    Streams and large responses
    ReadableStream and fetch streaming — when streaming earns its keep.
    15 min
  8. 08
    Real-time: WebSockets
    Two-way messaging, lifecycle, and reconnect patterns.
    15 min
  9. 09
    Real-time: Server-Sent Events
    When SSE beats WebSockets. EventSource, retry semantics, and the simpler half of real-time.
    12 min
  10. 10
    Observers and workers
    IntersectionObserver, ResizeObserver, MutationObserver, and Web Workers in one lesson.
    17 min

Prerequisites

  • · Comfortable writing JavaScript with promises and await
  • · Familiar with the DOM and event listeners
  • · Can read JSON and follow a small fetch example

After this, try